The invention is based on a fuel injection system generically defined hereinafter. A system of this kind, known from German Offenlegungsschrift No. 15 76 626, serves to supply fuel to an internal combustion engine that operates with externally supplied ignition and aspirates a fuel-air mixture. Fuel is pumped by a fuel feed pump into a reservoir kept at a constant fuel pressure. From this reservoir, via a throttle and an electromagnetic metering valve, the fuel that is to be injected is metered into an intermediate reservoir during the working stroke of the engine. The intermediate reservoir has a movable wall that yields to a soft spring; the biasing of the spring determines the injection pressure. This injection pressure will be lower in every case than the pressure in the first reservoir mentioned. During the intake stroke, finally, the metered fuel that has been pre-stored in the intermediate reservoir is delivered via second electromagnetic valve to the injection nozzle, which injects the fuel either into the intake tube of the engine or, during the intake stroke, into the combustion chamber.
In controlling the injection quantities for a high-pressure injection in self-igniting internal combustion engines, it is also known for the fuel injection quantity that is to be supplied per cylinder to be controlled by using a relief valve to determine the effective fuel supply provided by a reciprocating pump piston. A fuel injection system of this kind is disclosed in U. S. Pat. No. 3,851,635, in which an intermittently driven pump piston pumps fuel via a check valve into a collecting line, from which injection lines lead away to the individual injection nozzles. Each of these injection lines has a first magnetic valve, downstream of which a relief line branches off from the injection line, and a second magnetic valve is disposed in each relief line. The first magnetic valve serves to trigger the associated injection valve and is switched at the same time as the second magnetic valve, in such a way that the first magnetic valve opens and the second magnetic valve closes, so that an injection takes place. This system is intended in particular to increase the accuracy of the instants of injection.